A GTE includes a multistage axial compressor that pressurizes air and mixes the pressurized air with fuel. The mixture is directed into a combustor where it ignites, generating hot combustion gases that flow downstream through a high-pressure turbine. The turbine converts heat energy from the gases into mechanical energy. A portion of the mechanical energy is used to drive the compressor, while a remaining portion is directed offboard for other purposes. For example, the remaining portion of mechanical energy can be directed to drive a generator to produce electricity, to propel a vehicle, and/or to drive a compressing or pumping device.
Each stage of the compressor usually includes a row of spaced apart blades, each blade comprising an airfoil that extends radially outward from a supporting rotor hub. The airfoils are subject to high temperatures and high local stresses (e.g., bending and/or vibratory stresses) during operation. These stresses can cause cracks to form at a tip and/or attachment region of the airfoil. Unless otherwise accounted for, the cracks can result in GTE performance losses due to mechanical failure.
U.S. Pat. No. 7,497,664 (“the '664 patent”) describes a method and apparatus for reducing vibrations induced in compressor blades. According to the '664 patent, compressor blades can be designed to have a thickness profile that purportedly reduces cracking and facilitates the distribution of blade tip stresses over a larger area of the blade airfoil. The profile includes a maximum thickness that varies along a span of the airfoil according to a chord length of the airfoil.